Behavior

Richard E. Young

Behavior

Vampyroteuthis can swim surprisingly fast for a gelatinous animal. Hunt (1996) estimates from videotapes that it can reach two body lengths/sec, and it can accellerate to this speed in 5 sec. An escape reaction involves the quick movement of the fins toward the funnel followed by a jet from the mantle. This sequence is repeated as the vampire takes a series of quick turns in an erratic escape route (Hunt, 1996). The arms are sometimes spread forward to form, along with the web, an umbrella-like or bell-shaped posture while the vampire slowly swims forward (Hunt, 1996). The vampire appears to orient most commonly in a horizontal attitude with generally one filament extended (Hunt, 1996). The filaments appear to be tactile sense organs (Hunt, 1996). It has a posture ("pineapple posture") in which the arms and web are spread aborally over the head and mantle (Robison, 1995). In this posture the squid would be somewhat more difficult to injure and would be covered by a densely pigmented cloak. The oral surface of the arms and webs are the most heavily pigmented (black) regions on the animal. The posture, therefore, is probably a defensive one.

Hunt (1966) first observed bioluminescence displays in the living animal. Fin-base photophores have been observed to glow brightly for less than a second (a flash) or longer than two minutes. In addition the light intensity can vary giving a pulsating appearance, and as light is extinguished, the glowing disc can be seen to decrease in diameter as well as intensity.

Arm-tip organs are unpigmented on their oral surface where light is emitted but otherwise do not look like luminescent structures (see photograph on the right). The photophores all glow simultaneously, or they all can flash at a rate of one to three per second or pulsate. With the arm-tip organs apparently glowing continuously, the vampire moves the arms ("arm writhing") around rapidly exposing and hiding the photophores which is "...very disorienting [to an observer] when trying to visually fix the animal's position" (Hunt, 1996 p. 104). Often a flash of the arm tips is followed by a rapid escape response. Another unusual and visually confusing effect is seen when viewing the vampire posteriorly from the mantle apex. The apparently disturbed vampire can curl the arms and web posteriorly over the head ("pineapple posture") then illuminate the arm-tip organs and the fin-base organs. "...the arm tips appear to come toward you, whereas the fin[base]lights appear to be moving away (due to their apparent shrinkage)" (Hunt, 1996, p. 104).

The third source of bioluminescence is luminescent clouds. These appear as a mucous matrix with a few hundred to over 1000 discrete, glowing particles embedded in it. The particles can glow for up to 9.5 min. The source of the particles has been shown to be the arm tip organs (Robison, et al., 2003). The latter authors suggest that flashing of the arm-tip organs is controlled by covering or exposing the photogenic region by the pigmented sides of the arm tips, that the microscopic glowing particles are not luminescent bacteria, and that the function of the bioluminescence is to startle or distract a predator.

Some spectacular videos of Vampyroteuthis bioluminescence can be seen here: